FIG. 1 schematically illustrates a skid-steer loader having a diesel engine 10 driving two hydrostatic pumps 12 that pump hydraulic fluid to two hydrostatic motors 14 and 16. Motor 14 drives the wheels 18 on the left side of the loader and the motor 16 drives the wheels 20 on the right side. Right and left hand levers (not shown) enable an operator to vary the flow of hydraulic fluid to the motors 14 and 16 to thereby separately control the direction and rate of rotation of the wheels on each side of the loader. The engine also drives a gear pump 22 that supplies hydraulic fluid to boom cylinders 24 to raise and lower a boom (not shown) and to cylinders 26 to tilt a bucket (not shown) carried by the boom. A loader of the type shown in FIG. 1 is disclosed in the publication Operator's Manual, Skid-Steer Loader L565, LX565, LX665, Ford New Holland, Inc. (1993).
Experience has shown that certain types of diesel engines produced by some manufacturers present a problem when used in a loader as shown in FIG. 1 in that they may, if stalled under conditions of heavy backload, spontaneously restart in the reverse direction. This may occur, for example, if the loader is moving up an incline with a heavy load in the bucket, the operator "lugs" the engine so that it stalls, and the loader begins to drift backwardly down the incline. If the operator keeps the hand levers in the forward (higher forward speed) direction the energy of the wheels is coupled back to the engine through the motors 14 and 16, which now act as pumps, and the pumps 12, which now act as motors to drive the engine in the reverse direction. Because the engine is hot, the compression caused by the reverse drive causes fuel. ignition and the engine starts in reverse.
If the engine runs in the reverse direction, the air filter may be damaged in only a few seconds. Furthermore, the operator may adversely react if the loader moves unexpectedly in reverse.